The immune system is one of the most complex systems of our body. When our body is being faced with different conditions, it needs to protect itself from different dangers. It should be able to Identify and neutralize the foreign elements in the most appropriate manner. The main cells that are responsible for defending the body are leukocytes. In some people, the immune system may have certain gaps.

Microbes and Infection:The body is able to distinguish all foreign bodies and defend itself against them. All the problems that accompany the reaction of the body is known as the disease.When the foreign body is a microbe, the disease is considered to be infectious.

There are several types:Protozoa: Some are harmless while others are pathogens such as malaria plasmodium.Bacteria: is a unicellular organism

Infection:Internal body fluids (blood, lymph, cerebrospinal fluid) are rich in nutrients, oxygen and certain temperatures are conducive to the spread of bacteria.